Sunday, August 24, 2014

Before we start, I'd like to thank listeners Dim Questor, who posted another nice review on iTunes, and Jordan Mahoney, who shared our podcast link on Facebook. Remember, you too can have your name,or bizarre iTunes nickname, immortalized in my podcast by following in Dim or Jordan's shoes!

Now, on to today's topic. You may have heard some online skeptics derisively referring to the "precautionary principle", the idea popular among certain activists that if a new technology has any risks at all, or some new product has a nonzero amount of toxic contamination, we need to take the safe path and ban it. While a certain level of caution is always wise, the fact is that anything you do contains some level of risk, and any product contains some level of contamination. For example, we all still ride in cars, even though an average of 0.72 people die for every 100 million passenger miles driven in cars. Should cars be banned because this number in .72 rather than 0? If we were to follow this principle in general, we would effectively prevent all forms of scientfic and technological advance. So I was surprised to see some buzz on the internet indicating that Nassim Nicholas Taleb, a famous mathematical philosopher who has written several books on risk and probablility, and who I respect a lot, has been arguing that the Precautionary Principle needs to be applied to the concept of genentically modified foods, or GMOs, and that they should therefore be banned. I downloaded his paper, linked in the show notes, to learn a little more about this somewhat surprising position.

Let's begin by reviewing Taleb's "Black Swan" concept, which you may remember me intruducing back in podcast 84, "How to Bankrupt Your Boss And Get Rich". The idea here is that when managing risk, we have to consider both the probablility of a negative event, and the magnitude of its effect. If a low-probablility event, known as a Black Swan, causes a huge penalty, this may outweigh all the cumulative benefits of taking a risk over time. For example, suppose we make a bet that we will flip a coin once per month, and I have to pay you $100 for each head, and you pay me $1000 for each tail. There are risks to each coin flip- I might gain or lose money- but not much overall risk to me by playing this game, since it's nearly impossible to lose a lot of money, and in the long term I will profit nicely on average.

Now suppose we add a new rule: if we see the "black swan" event of five heads in a row, I need to pay you a million dollars. With this rule, the game has changed a lot. If a certain low-probability but not impossible result happens, I will be totally ruined, losing more money than I have ever won in this game. The expected number of tosses to get 5 heads in a row is about 62, so even though it might seem like a profitable game for a year or two, I'm virtually guaranteed to be ruined in the long run. Of course this game is pretty silly, but as Taleb has pointed out, many traders of complex derivatives in the stock market are essentially playing it: they please their bosses by showing steady market-beating profits, and collect their annual bonuses, until one day some low-probability Black Swan event causes them to lose their company much more money than their accumulated total profits. Often by that point they have built up enough savings so they don't care if they are fired.

The Black Swan concept goes beyond finances, of course, which is where the GMO discussion comes in. Taleb points out that when taking any action which provides risk of global ruin, we need apply the Precautionary Principle, because when you multiply a small probability risk by the infinite costs of the global ruin scenario, you can see that the risk just isn't worth it. In other words, in cases where the cost is total ruin, the Precautionary Principle should apply, and we should refuse to take any risk, no matter how small it seems. We need to be careful here, though, in that Taleb is not advocating a universal embrace of the precautionary principle, but just advocating it for very specific scenarios. He still rides in cars and planes, for example. He also continues to support nuclear power, because even though a nuclear meltdown is not good, the risks are all local: a single nuclear accident, though bad for the immediate area, will not blow up the planet, and thus can be planned for within the domain of normal risk management.

If I'm reading Taleb's paper correctly, his main concern with GMOs is that large near-monopoly companies are selling newly existing forms of life to a global market, and in effect creating a monoculture, where a huge proportion of the world's crops in each category are a single, globally genetically identical species. Furthermore, these are new species, lacking the centuries of farming experience we have with naturally existing ones. This means that we have a high risk of problems with these new species, and many such problems carry risk of infinite-cost global ruin. If it has hidden long-term effects on human health, nearly the whole planet will be affected at once. If it is capable of virally spreading and displacing other species, this will all happen at once worldwide. And if some new disease can kill this species of crop, it will devastate the whole world's food produciton. Thus we are taking an infinite potential cost, which can affect agriculture or humanity worldwide, and offsetting it against a marginal benefit of improved crops due to the GMO. Incurring the risk of an infinite-cost Black Swan event, for a finite benefit due to GMO crops, does not balance out mathematically, and thus we shouldn't do it.

It seems to me that his most compelling point is really about the risk of monoculture- having a tiny set of large companies as global seed suppliers- rather than the risks of GMOs themselves. If Monsanto disavowed GMOs in favor of old-fashioned selective breeding, this monoculture issue would still be present. In general, Taleb has good points about monopolies and central control-- we do need to be careful about transforming local risks to global ones by making things the same everywhere. This is similar to his critique of the economic theory of Comparative Advantage, which we discussed back in episode 165. We need to watch for and prevent a true worldwide dependence on a tiny set of near-genetically-identical species, and make sure any new species is extensively tested in a small, local environment before being propagated further. And we do need to make sure we never reach a point where too large a proportion of the world is dependent on a single species of crop. But as long as we are taking action to avoid this worldwide monoculture, the concept behind GMO foods is basically the same as traditional selective breeding-- producing a new species based on existing forms of life-- so it's hard for me to see why it should be treated so differently. Many new plant varieties have been developed and deployed based on selective breeding over the past century as well.

Whether GMOs truly provide a risk of global ruin, or really just a finite risk of some bad crops in local markets, becomes even more important when we balance these risks against the potenital benefits. Improving overall crop yields and nutritional value, one of the potential GMO benefits, is a life-or-death question for many impoverished populations worldwide. Nobel Peace Prize winner Norman Bourlaug, known as "the man who saved a billion lives" due to his work improving the yields of Third World agriculture, stated before he passed away that we are approaching natural limits in making use of arable land, and that GMOs would be required in addition to fully end world hunger. Taleb dismisses such GMO benefits because we could theoretically solve the problems through other means-- but I don't think it's valid to argue on the basis of what can be theoretically done, if nobody is currently doing it. Our society, markets, and culture currently have the will and ability to solve these problems through the careful use of GMOs, and are not doing it through other methods suggested by Taleb.

So, should we follow Taleb's recommendations and ban GMOs, due to the imbalance of a finite benefit vs an infinite risk? Or embrace GMOs with open arms and dismiss Taleb as a kook on this issue? Neither is quite right. I think Taleb does have a good point about the risks of monoculture, and we need to make sure we create policies that ensure agricultural variety, and prevent reaching a point where nearly the whole world is depending on a fragile handful of plant species. But it looks to me like as long as we avoid this pitfall, the other risks of GMOs are comparable to those of naturally bred species, and the potential benefits are massive, potentially saving millions of starving and malnourished people. Thus we need to think carefully about all the benefits involved, and the true level of risk, before taking any hasty government action.

Sunday, August 3, 2014

Before we start, I'd like to thank listener Dan Unger, who posted another nice review on iTunes. Thanks Dan!

Now, on to today's topic. Most of us know the name of Louis Pasteur, the 19th-century French biologist and chemist, from seeing his name embedded in the term 'pasteurized' on milk cartons. And he is rightly remembered for his discoveries in the area of the germ theory of disease, which led to the development of many vaccines as well as the famous process for heating milk to reduce the bacterial content, collectively saving human lives in the millions over the past two centuries. But did you know that before his famous medical contributions, he made an equally revolutionary discovery in chemistry: the fact that molecules could posses chirality, that is left-handedness or right-handedness, just like ordinary macroscopic 3-D objects?

We're all familiar with the concept of left/right asymmetry in the real world. Simple examples are a glove, which cannot be changed from left-handed to right-handed without turning it inside out, or an ordinary screw, where we have to remember the "lefty loosey righty tighty" rule to use it properly. It seems natural that molecules should be able to exhibit such asymmetry as well, but at the dawn of the 19th century, scientists hadn't really discussed that idea much. In 1848, a young Louis Pasteur was studying a chemical called tartaric acid, a byproduct of wine production. He was trying to understand a strange anomaly related to this substance and a very similar one called racemic acid. Scientists had determined the chemical compositions of both acids, and they were exactly the same. Yet they had some very different physical properties: in particular, tartaric acid in solution would rotate a beam of polarized light passing through it, while racemic acid had no such effect.

Pasteur decided that there must be some geometric difference at the molecular level, so generated crystals of both acids to examine under a microscope. Remember that crystals are essentially an endless repetition of a small molecular structure, so studying the shapes of pure crystals can grant some insight into the shapes of the molecules themselves. Other scientists thought he was wasting his time, since the experiment had already been done by others, and they found that tartaric and racemic acid crystals were exactly the same shape. But Pasteur noticed something that his colleagues had missed: while tartaric acid crystals were all the same shape, racemic acid was a mixture of two types: the tartaric acid crystals, plus another form that was a mirror image of the other. Since the form was somewhat asymmetric, this meant that the two forms were truly different, even though other scientists had dismissed these differences as insignificant: no rotation in our physical space could transform one into the other.

Pasteur then came up with a clever experiment. He crystallized some racemic acid, then with a microscope and needle, carefully separated the left-handed and right-handed crystals into two piles. Then he created solutions of the two types of crystals. As he suspected, one of the solutions was a solution of tartaric acid, and rotated polarized light in the same way that tartaric acid normally would. But the other was a new substance, which rotated light in the opposite direction. In other words, the reason racemic acid did not usually bend light was that it was a mix of right-handed and left-handed molecules, while tartartic acid consisted purely of the left-handed form. Pasteur had separated out the right-handed component of the racemic acid. The result was so shocking to the scientists of the day that the French Academy of Sciences made Pasteur repeat the experiment in front of witnesses before they would accept it.

Today awareness of the chirality, or handedness, of molecules plays a critical role in biochemical and medical research. This is mainly due to the fact that life is "homochiral", a fancy way of saying that our basic building blocks all have a single handedness. This differs from most naturally occurring nonliving materials, which tend to exhibit both kinds of handedness randomly in roughly even proportions. The biological origin of Pasteur's tartaric acid was responsible for its one-sided content. Almost all amino acids found in living creatures are left-handed, and we use them to interact with right-handed sugars to supply most of our energy. At first, scientists found this very surprising, since attempts to artificially synthesize most biological molecules result in roughly equal quantities of right- and left- handed forms. This can have tragic consequences: the infamous pregnancy drug thalidomide was a great treatment for morning sickness in its left-handed form, but the right-handed version caused serious birth defects.

The reason for life's left-handedness is one of science's great mysteries. You can see links to articles in the show notes with a few different theories. One is that it stems from a fundamental left-handedness in physics, since certain types of radioactive decay have a leftward electron spin. The effect is tiny, though, and you could argue that this is just begging the question, since you still have to explain the left-handedness of physics. Another theory is that life was seeded by left-handed molecules from space: meteors with both types of amino acids may have happened to pass through regions of space with polarized light that destroyed one kind more often than the other. Or it could just be luck-- maybe left-handed life randomly formed first in the primordial soup, and once it had a toehold it crowded out any other possibilities. Whatever the real answer is, this geometry is critically important to every cell in our bodies.

Note that this podcast is intended mainly for audio consumption, so you will not see the numerous illustrations & diagrams you would find at most math sites, though these are linked in the show notes whenever possible.

The Math Mutation Book

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